3.1. Performance Characteristics
Basic engine performance metrics such as BTE and BSFC were determined in this experiment for blends of microalgae biodiesel and compared with results obtained using petro diesel fuel.
Figure 4 depicted the fluctuation in brake thermal efficiency versus engine load. As compare to petro diesel fuel mode, brake thermal efficiency decreases with fuel blends type as the load on the engine alters plus increases with the engine load rises. The specific fuel consumption increases as the calorific value declines in the microalgae fuel blends mode, affecting the brake thermal efficiency. Additionally, when the percentage of blended fuel increases, the fuel's calorific value drops, leading to decreased rate of heat release and, ultimately, a fall in the engine's brake thermal efficiency (Kalsi SS et.al. 2017). In contrast to diesel fuel, there is a 2.41 percent reduction in brake thermal efficiency for MAB10 and a 7.14 percent drop in brake thermal efficiency for MAB50. BTE rises as engine load rises, and previous study has found similar trends. (Elsanusi OA et.al. 2017; Datta A et.al.2017; Srihari S et.al. 2017; Can O et.al.2017).
BSFC is influenced directly by the test fuel's heating value. The impact of heating value in fuel complete combustion cannot be overstated. Because biodiesel and their blends bears a lower heating value, they have a direct impact on brake specific fuel consumption. Figure 5 depicts the BSFC's behavioral variability as a function of the engine's loading. The plot clearly shows that BSFC is the lowest-cost diesel fuel, followed by all microalgae biodiesel mixes at such loads. When compared to diesel fuel, the BSFC of MAB10 enhanced by 3.43 percent and MAB50 increased by 11.54 percent. Figure 5 shows that BSFC decreases with greater load for each microalgae biodiesel blend because combustion efficiency increases. In a cited study (Srihari S et.al. 2017; Can O et.al.2017; Gorji RM et.al. 2017), a similar trend of result was seen.
3.2. Emission Characteristics
In this experimentation for microalgae biodiesel blends and diesel fuel, engine exhaust emission characteristics such as CO2, NOX, HC and CO gas emissions were determined in this experiment in accord with various loads placed on the test engine and compared to petroleum diesel fuel.
The elements that determine CO2 emissions from engine exhaust include viscosity, atomization process, CR, oxygen, engine rpm, and so on (Celik M et.al. 2017; Rahman SMA et.al. 2013; Gharehghani A et.al.2017; Muralidharan K, et.al. 2011). Figure 6 shows the variance in CO2 emissions as a function of engine loading for studied fuels: petroleum diesel, MAB10, MAB20, MAB30, MAB40, and MAB50. In comparison to diesel, the CO2 content of microalgae biodiesel blends was found to be greater.
The temperature of combustion, the oxygen concentration of the fuel along with the actual space of the combustion zone were the elements that directly influence NOX emissions (Zehra S et.al.2014). Different elements that influence NOX exhaust emissions include stoichiometry, temperature of flame, delay in ignition, fatty acid composition, heat removal rate (HRR), premixing, cetane number, injection timing as well as thermo-physical properties of the fuel (Rajak U et.al. 2018; Shrivastava P et.al. 2019; Subhaschandra ST et.al.2019). In accordance with engine loads, Fig. 07 depicts NOX exhaust emission fluctuations for microalgae biodiesel blends and petroleum diesel fuel. It has been witnessed that when the load on engine increases, so does NOX exhaust output increases. In comparison to petroleum diesel fuel, NOX emissions from Microalgae Biodiesel mixes were thought to be higher.
Figure 8 shows how hydrocarbon exhaust emissions vary depending on engine load for all microalgae biodiesel blends as well as petroleum diesel. MAB10 Microalgae Biodiesel Blends reduced HC emissions by 9.2 percent compared to diesel fuel, 20.58 percent compared to MAB20, 29.62 percent compared to MAB30, 23.84 percent compared to MAB40, and 13 percent compared to MAB50 Microalgae Biodiesel Blends. Figure 8 shows how increasing the blending % in diesel fuel affects HC emissions. This could be linked to biodiesel blends' higher kinetic viscosity, which slows fuel atomization and hence reduces HC emissions (Çelikten I. et.al 2012).
Figure 9 depicts the changes in CO exhaust emissions for all tested microalgae biodiesel blends and petroleum diesel fuel under various engine loading levels. The CO exhaust emission is least for increasing engine loading for all the fuels evaluated, according to the observations.
Biodiesel and its blends are oxygenated fuels that allow for complete combustion which allows conversion of CO to CO2 molecules, resulting in significant decline in CO emissions as compared to petro diesel (Çelikten I. et.al 2012). The average decline in CO emission was 7.7% for MAB10, 16.8% for MAB20, 12.60 percent for MAB30, 13.30 percent for MAB40, and 14.54 percent for MAB50 when compared to diesel fuel.